A filter element is proposed comprising a pleated filter element of paper or non-woven fabric in the form of a plate fixed in a frame. German Patent 40 02 078 discloses a filter element. This consists of a nonwoven fabric material folded in zig-zag form which is provided with frame elements, the frame elements being produced in part by thermoplastic welding of the nonwoven fabric. Such a filter element is used, for example, in automobile manufacture. A disadvantage of this filter element is to be seen in the fact that it shows a certain instability. Especially in the event of pressure surges there is the danger that the pleats may buckle or collapse. The filtering action is thus considerably reduced, and the filter's resistance to flow is greatly increased.
To avoid these disadvantages, it is known from U.S. Pat. No. 2,058,669 to provide a filter element folded in zig-zag form with a supporting comb. This supporting comb is adapted to improve the stability of the folds considerably. However, a disadvantage of the supporting comb is to be seen in the fact that the effective filter surface is very greatly reduced.
The invention is addressed to the problem of providing a filter element which avoids the aforementioned disadvantages, exhibits great stability, and at the same time produces only an insignificant increase in the resistance to flow. Moreover, the filter element should be simple to dispose of.